1. Field of the Invention
This invention relates to substituted 9-(1 or 3-monoacyloxy or 1,3-diacyloxy-2-propoxymethyl)purines and pharmaceutically acceptable acid addition salts thereof which are useful as antiviral agents. The invention also relates to a pharmaceutical composition containing the above compounds in combination with a suitable non-toxic carrier, the composition being useful in combatting viral infections. The invention also relates to a process for preparing the compounds of the invention.
2. Related Disclosure
Viral infections are widespread and result in a wide variety of symptoms. Some viral infections are easily overcome by the body's defense mechanism, but when this defense mechanism is impaired these infections can lead to permanent damage, e.g., blindness, and even to death. One such family of viruses which may cause serious infections is the herpes virus group.
The drugs presently used to treat viral infections are ineffective in many cases or, if effective, are needed in large and/or continuous dosages which produce serious side-effects and/or toxicity. Therefore there is a need for an effective antiviral agent which is effective at lower dosages than the presently available drugs, thus diminishing the chance of possible side-effects and toxicity.
U.S. Pat. No. 4,199,574 discloses compounds represented by the following generic formula: ##STR2## wherein X is sulphur or oxygen, R.sup.1 is hydrogen, halogen, hydroxy, alkoxy, azide, thio, alkylthio, amino, alkylamino or dialkylamino; R.sup.2 is hydrogen, halogen, alkylthio, acylamino, amino or azide; R.sup.3 is hydrogen, straight or branch chain or cyclic alkyl, hydroxyalkyl, benzyloxyalkyl or phenyl; R.sup.4 is hydrogen, hydroxy or alkyl; R.sup.5 is hydrogen, hydroxy, amino, alkyl, hydroxyalkyl, benzyloxy, benzoyloxy, benzoyloxymethyl, sulphamoyloxy, phosphate, carboxypropiamyloxy, straight chain or cyclic acyloxy having from 1 to 8 carbon atoms e.g., acetoxy or substituted carbamoyl group of formula NHCO-Z wherein Z is alkyl, aryl or aralkyl optionally substituted by one or more of sulphonyl, amino, carbamoyl or halogen; R.sup.6 is hydrogen or alkyl, provided that when X is oxygen and R.sup.2, R.sup.3, R.sup.4, and R.sup.6 are hydrogen, R.sup.1 is not amino or methylamino when R.sup.5 is hydrogen or hydroxy, or a salt thereof.
The class of compounds represented by the above formula and the pharmaceutically acceptable acid addition salts thereof are described to exhibit antiviral activity. See also Tetrahedron Letters, 21, 327-30 (1980), U.S. Pat. No. 4,294,831 and U.S. Pat. No. 4,347,360.